This invention relates to wheelchairs, and more particularly to an apparatus for propelling a wheelchair. More particularly, this invention relates to a wheelchair having a hand-operable drive ring mounted separately from the drive wheel.
Wheelchairs and invalid chairs are well known and typically consist of a chair frame disposed between two sets of rear and front wheels with the rear wheel acting as the drive wheel and the front wheel being castered or rotatable to allow for turning the chair. In standard wheelchair construction, the rear drive wheel is designed to be directly engaged by the occupant's hands to propel the chair or a separate ring is mounted about the same axis of rotation as the drive wheel for the occupant to use to propel the drive wheel.
According to the current design of wheelchairs, the occupant's hands, arms or clothes may come in contact with the ground-engaging surface of the drive wheel resulting in the transfer of debris to their hands or clothes.
In some alternative designs of wheelchairs, a hand wheel is mounted to the frame of the wheelchair and this hand wheel rotates about a separate axis which is located above the axle of the drive wheel. These hand wheels have an outer rim which is connected by a spoke or series of spokes to a hub that is rotatably mounted to an axle. The hub or axle is then coupled by a belt or chain to the drive wheel so that rotation of the hand wheel will cause rotation of the drive wheels. The spokes of these separate hand wheels or the hub upon which the rim is mounted may interfere with the user grasping the rim when attempting to propel the wheelchair. Occupants may need to be cautious in selecting their hand location on the hand wheel or may need to modify their grips to accommodate the spokes or hubs of the hand wheel.
According to the present invention, an apparatus for propelling a chair across a surface upon which the chair rests consists of a chair frame suitable for occupancy by a person having propulsion mechanisms attached to and partially extending below the chair frame to engage the surface for propelling the chair frame across the surface upon which the chair rests. A spokeless propulsion control ring is rotatably mounted to the chair frame entirely above the surface-engaging portion of the propulsion mechanism and is coupled to the propulsion mechanism so that rotation of the spokeless propulsion control ring activates the propulsion mechanism.
In the described embodiments, the apparatus for propelling a chair across a surface has a chair frame with a seat disposed between the sides of the chair frame and a set of rear drive wheels rotatably mounted on separate axle pins on opposite lower rear sides of the frame. A pair of castered or rotatable front wheels are attached on opposite sides of the lower front portion of the frame to engage the surface and aid in steering the chair. A pair of spokeless propulsion control rings or power rings are rotatably mounted on opposite sides of the chair to rotate about an imaginary axis located above the axis of the axles about which the drive wheels rotate. The power rings are mounted to the chair using a plurality of pinch rollers rotatably mounted to each side of the frame and arranged to define planes of rotation and axes of rotation for the power rings.
The pinch rollers are oriented so that the portion of the roller which engages the power ring is located on a circle concentric about the axis of rotation of the propulsion control ring. Sufficient rollers are provided to define and restrict the motion of the power rings to a circle about the axis of rotation of the power rings.
At least one of these pinch rollers, known as the drive pinch roller, on each side of the frame is provided with a pulley for coupling the drive pinch roller, and therethrough its associated power ring, to the drive wheel of the chair. A continuous loop coupler such as a belt or chain extends between the pulley on each drive pinch roller and a pulley on the axle of its associated drive wheel. Thus, rotation of the power ring induces rotation of the drive pinch roller which in turn, through the continuous loop coupler, induces rotation of the drive wheel causing the chair to move across the surface upon which it sits.
Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.